Simcenter Testing Solutions Alias Mapping: Matching Geometry to Test Measurement Data

Direct YouTube link: https://youtu.be/lRxHeaQzyVs

 

Imagine you've been acquiring vibration data all day... while analyzing, your boss suggests animating an operational deflection shape with the data.

The only problem is that you did not use the same naming convention on the Simcenter Testlab geometry as you did with the test data. Or even worse, the data was stored without suitable names and directions for a geometry animation.

Previously, if these names did not match, either the geometry names or the data names would have to be altered to match. That’s a lot of renaming just to animate a shape, especially if a lot of different runs and configurations were tested!

Figure 1: When the modal data node names and the geometry node names do not match an error is generated: “No matching nodes found – Check alias table”.

As of Simcenter Testlab Version 17 and higher, an alias table (similar to a lookup table) has been introduced so that mapping can be done between the geometry and the modal data. This makes it possible to animate shapes without altering node names. Note; Simcenter Testlab was formerly called LMS Test.Lab.

Example of using alias table: modal analysis of a golf club

Imagine conducting an impact test on a golf club. Data is taken in the X and Y directions at eleven points along the physical club. FRFs are calculated for all the runs and it is now desired to animate mode shapes in Simcenter Testlab.

Figure 2: A CAD model of the golf club with accelerometers represented with yellow dots. Data was taken in the X and Z directions at all accelerometer locations.

A simple geometry is created in Simcenter Testlab that matches the accelerometer locations on the physical object in Figure 2 above.

Figure 3: A wireframe geometry of the golf club is created. Each node represents an accelerometer location.

The node names between the geometry and the modal data do not match. Rather than renaming all of the nodes in the geometry or in the data, an alias table is created. The alias table links the node names in the geometry to the node names from the modal data. This way the software can animate nodes on the geometry with the appropriate data (despite the geometry name and the data name not matching).

In the Navigator worksheet of Simcenter Testlab, open the alias mapping table by right clicking on the project name in the project tree and selecting "Add/Edit Alias Mapping".

Figure 4: Right click on the project name and the click “Add/Edit Alias Mapping”.

The alias data and the original data must both be selected and mapped.

First, from the upper left, choose the "Active Project Geometry" as the alias data. The test measurement data will be mapped onto the selected geometry nodes.

Figure 5: The alias mapping window.

Select the directions that need to be alias mapped. In this case, only the X, Y, and Z directions are of interest. Click “Replace”. This will import all of the geometry nodes and selected directions.

Figure 6: Chose the directions and import the geometry data.

Next, import the source measurement data that the geometry is to be mapped to. Using the selections in the upper right of the menu, this can either be from the active project or from the input basket. In this case, all the runs from a section in the active project are imported.

Figure 7: Select the original data and click “Replace” to import it.

Now the mapping must be completed. In this case, only the +X and +Y directions must be mapped (because data was only taken in the +X and +Y directions).

So, in the “Quick find” filter, search for +X in both the alias data and the original data.

Figure 8: Easily parse through data using the quick find feature. Any character can be searched on.

Knowing that “golfclub1:+x” in the geometry is equivalent to “club1:0+X” in the test data, these two nodes can be matched. Enter the nodes into the alias table by selecting the node from the list and then clicking the “Add” button. Repeat this for both the alias data and the original source data.

Figure 9: Mapping the nodes to one another and populating the alias table.

Repeat this process until all necessary nodes are mapped.

Figure 10: Map all nodes between the geometry and the test data.

NOTE: It is possible to copy and paste the alias table to / from excel. This would allows saving and restoring different configurations.To de-activate the alias table, highlight all the filled cells, right click, and choose "Clear".

When the status is green and "Everything OK" message appears, press the "OK" button to continue.

Once all the nodes are mapped, it is possible to continue with the operational deflection shape or modal analysis and successfully animate shapes.

Figure 11: Animate mode shapes on the geometry.

NOTE: ALWAYS create the alias table before doing any modal analysis processing. The alias table will not override existing processing, it will only work for new processing.

The alias table makes linking the data names to the geometry names easier than ever!

Questions? Email charles.rice@siemens.com or contact Siemens Support Center.

Modal Analysis and Operational Deflection Shapes links:

• Index of Testing Knowledge Articles
• Natural Frequency and Resonance
• What is Frequency Response Function (FRF)?
• How to calculate damping from a FRF?
• Modal Testing: A Practical Guide
• Getting Started with Modal Curvefitting
• Modal Assurance Criterion
• Simcenter Testlab Modal Analysis: Modification Prediction
• Import CAD into Simcenter Testlab
• Animate CAD Geometry
• Alias Table: Mapping Test Data to Geometry
• Geometry in Simcenter Testlab
• Simcenter Testlab: Multi-Run Modal Analysis
• Maximum Likelihood estimation of a Modal Model (MLMM)
• Difference Between Residues and Residuals?
• What is an Operational Deflection Shape (ODS)?
• What is Operational Modal Analysis (OMA)?
• Making a Video of a Time Animation
• Modal Testing Seminar
• Modal Analysis and FEA-Test Correlation Seminar
• Modal Analysis YouTube Playlist